1. air pollution (both man made and natural such as volcanic gases)
2. airborne salt spray or droplets
3. temperature
4. and moisture.
The presence of industrial pollutants in the polar ice caps demonstrates that even the most remote corners of the Earth are not immune to its effects. Nitrogen and sulfur compounds can form acids when discharged or acidic material may be released to the atmosphere directly by some industries accelerating the corrosion process on metal these substances encounter. Of course urban areas and those areas in close proximity to or downwind from "smokestack type" industries and power plants are subject to the most corrosive effects of airborne pollution.
Salt spray and airborne saltwater droplets introduce chloride ions to metal surfaces with a corresponding deleterious effect on the metal. But one does not have to live on the beach to experience these corrosive effects as it is estimated that airborne sea spray saltwater micro droplets can carry as much as 7 miles inland from the coast. The presence of moisture is an absolute necessity for most corrosion processes and when combined with elevated temperatures and salt or pollutants further enhances the atmospheric corrosion process.
Atmospheric corrosion is ubiquitous and is responsible for more metal damage (both on a cost accounting basis and an actual quantitative basis) then any other form of environmental corrosion. After all, everything on the Earth's surface is exposed to the atmosphere be it vehicles, buildings, bridges, etc.
histories:
When exposed to the Earth's atmosphere under the typical conditions, most metals have a tendency to slowly return to their natural state......as a metallic ore.
(NOTE: The only metals which do not commonly corrode under the average conditions present at the Earth's surface are gold, platinum and palladium.)
Example: Iron in auto body steel exposed to the atmosphere "oxidizes" and changes back to Iron Ore (Ferric Oxide Fe2O3).......better known as rust. Corrosion causes nearly 400 billion dollars in damage in the U.S. alone each year and it is estimated that most nations spend about 5% of their total income in combating or repairing corrosion damage.
Salt spray and airborne saltwater droplets introduce chloride ions to metal surfaces with a corresponding deleterious effect on the metal. But one does not have to live on the beach to experience these corrosive effects as it is estimated that airborne sea spray saltwater micro droplets can carry as much as 7 miles inland from the coast. The presence of moisture is an absolute necessity for most corrosion processes and when combined with elevated temperatures and salt or pollutants further enhances the atmospheric corrosion process.
Atmospheric corrosion is ubiquitous and is responsible for more metal damage (both on a cost accounting basis and an actual quantitative basis) then any other form of environmental corrosion. After all, everything on the Earth's surface is exposed to the atmosphere be it vehicles, buildings, bridges, etc.
histories:
When exposed to the Earth's atmosphere under the typical conditions, most metals have a tendency to slowly return to their natural state......as a metallic ore.
(NOTE: The only metals which do not commonly corrode under the average conditions present at the Earth's surface are gold, platinum and palladium.)
Example: Iron in auto body steel exposed to the atmosphere "oxidizes" and changes back to Iron Ore (Ferric Oxide Fe2O3).......better known as rust. Corrosion causes nearly 400 billion dollars in damage in the U.S. alone each year and it is estimated that most nations spend about 5% of their total income in combating or repairing corrosion damage.
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